Two-phase fluid distribution properties in the shell side of spiral wound heat exchangers under the coupling effect of operating and oscillatory factors

The fluid distribution performance in the shell side of spiral-wound heat exchangers is complex, especially under the coupled influence of operating and oscillatory parameters. To elucidate the underlying flow mechanisms, experiments were conducted under varied conditions. The flow patterns in the shell side of spiral tubes under oscillatory conditions were obtained. The results suggest that a vapor quality around 0.1 corresponds to a flow-pattern transition condition. As vapor quality increases from 0 to 0.1, the initial gas shear exerts only a limited influence on liquid columns. When vapor quality attains 0.2, the enhanced gas shear substantially reduces both the size and total volume of the liquid columns. Below a vapor quality of 0.1, the effects of mass flow and vapor quality on distribution performance are small; nevertheless, above this threshold, their impacts become markedly pronounced. The distribution performance deteriorates with low mass flow and long oscillatory periods, but improves with high mass flow and short periods. Notably, at vapor qualities above 0.1, intensified gas shear amplifies the adverse effect of prolonged oscillation. Sensitivity analysis quantifies the contribution of each parameter to distribution performance, yielding values of 49% for vapor quality, 38% for oscillatory period, and 13% for mass flow. Two strategies are proposed to control distribution performance under oscillatory conditions. The results obtained in this work provide useful guidance for the operation of spiral-wound heat exchangers.